Zebra Technologies WPT-3200 Users manual
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Infrastructure Placement Guide
WHEREPORT PLACEMENT
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WherePort Placement D0116 rev A1
Copyright WhereNet Corp. 2001
WhereNet - Confidential
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Infrastructure Placement Guide
Table of Contents Page
5 WHEREPORT PLACEMENT 4
5.1 OVERVIEW 4
5.2 MAGNETIC COMMUNICATION 5
5.3 APPLICATION STRATEGIES 8
5.4 WHEREPORT INSTALLATION 13
Table of Figures Page
FIGURE 5-1 BEST PERFORMANCE TAG- WHEREPORT ORIENTATION 6
FIGURE 5-2 WHEREPORT COVERAGE AREA 10
FIGURE 5-3 TYPICAL WHEREPORT PHASE SETTINGS 11
FIGURE 5-4 POWER AND PHASE SWITCHES 15
FIGURE 5-5 SIGNAL AND POWER WIRING 17
Table of Tables Page
TABLE 5-1 TYPICAL WHEREPORT RANGE 12
TABLE 5-2 SWITCH SETTINGS 14
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WherePort Placement D0116 rev A1
Copyright WhereNet Corp. 2001
WhereNet - Confidential
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Infrastructure Placement Guide
NOTICE
This device complies with part 15 of the FCC rules. Operation is subject to the
following conditions: (1) This device may not cause harmful interference, and (2) this
device must accept any interference, which may cause undesired operation.
Changes or modifications not expressly approved by the manufacturer could void the
user’s authority to operate the equipment.
This equipment has been tested and found to comply with the limits for a Class B
digital device, pursuant to part 15 of the FCC Rules. These limits are designed to
provide reasonable protection against harmful interference in a residential installation.
This equipment generates, uses and can radiate radio frequency energy and, if not
installed and used in accordance with the instructions, may cause harmful interference
to radio communications. However, there is no guarantee that interference will not
occur in a particular installation. If this equipment does cause harmful interference to
radio or television reception, which can be determined by turning the equipment off
and on, the user is encouraged to try to correct the interference by one or more of the
following measures:
- Reorient or relocate the receiving antenna.
- Increase the separation between the equipment and receiver.
- Connect the equipment into an outlet on a circuit different from that to which the
receiver is connected.
- Consult the dealer or an experienced radio/TV technician for help.
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WhereNet - Confidential
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Infrastructure Placement Guide
5 WHEREPORT PLACEMENT
5.1 Overview
In most WhereNet location applications, the WhereTag ID (tag) is set to blink at a
rate that is a compromise between battery life and the desire to know location
expeditiously. In many cases higher blink rates are used so critical events are not
missed by the location system. This adversely effects tag battery life. If the other side
of the compromise is selected, critical events that the customer wants the system to
track may be missed such as loading a tagged pallet into a departing truck. In this case
the pallet would simply disappear from the system without the knowledge of what
happened to it; is it a tag failure or is it gone?
The WherePort offers a method to ease this compromise and in many applications,
increase functionality of the system as a whole. To do this, it generates magnetic
signaling that is received by WhereTag ID (tag). When the tag receives the WherePort
signal, it blinks at a fast rate for a short period of time. The system receives the tag
signal and decodes not only the tag ID but also the ID of the WherePort unit(s) that
caused it to blink. Just as we call the tag transmission to the infrastructure a “blink”,
for ease of discussion, the term “ping” will be used for the WherePort to tag
communication. The WherePort ID can be used in many ways in installation design
but it is not intended as the primarily location tool, that remains the location system.
The WherePort is set by switch at installation to any of 8 IDs.
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WhereNet - Confidential
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Infrastructure Placement Guide
Because magnetic signaling is used, the range is about 20 feet maximum and can be
adjusted by switch at installation to shorter ranges. Magnetic signaling is used instead,
of RF or IR, so the range and performance of the communication to the tag is very
predictable. Rain and moisture does not effect it. Unlike RF, it will pass through thin
metal film enclosures like anti-static bags. Sparse metal sheets and objects do not
effectively block the magnetic signal, neither is it absorbed in a buildings structural
material, as is RF. The tag can be shielded from the signal though, so reasonable tag
mounting is required.
The WherePort is for indoor and outdoor installation. It requires a 24VAC power
source but may be powered from DC with certain performance limitations.
5.2 Magnetic Communication
Signal Coverage
It is very difficult to shield or stop the communication link to the tag as in trying to
limit the coverage area of the WherePort to a specific spot. This limitation will
become clearer as you begin to look at WherePort installations. Also impacting this is
that the WherePort produces a signal that surrounds it. That is, the signal coverage
behind it is about equal to that in front of it. With the range in front of the unit at 20’,
the range to the rear is nearly equal, decreasing slightly to the sides. The power level
of the WherePort is adjustable so the range can be reduced, but it is reduced
everywhere around it equally. In some very limited installations, one can take
advantage of the structural elements of the building to limit the coverage area. For
example, mounting the unit to the broad face of a 20” steal I-beam will reduce the
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WherePort Placement D0116 rev A1
Copyright WhereNet Corp. 2001
WhereNet - Confidential
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Infrastructure Placement Guide
coverage on the opposite side of the I-beam. Unfortunately, the I-beams are not
usually where you can take advantage of them and anything smaller has little effect.
Very large metal objects like cars and trucks can substantially block the signal.
Orientation Dependence
The magnetic communication system is sensitive to the orientation of the tag with
respect to the WherePort. Figure 5.1 shows the tag orientations relative to the
position of the WherePort that gives full range performance.
Optimum Tag Orientation
Not Optimum
45 Degrees Out
90 Degrees Out
Figure 5-1 Best Performance Tag- WherePort Orientation
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WherePort Placement D0116 rev A1
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WhereNet - Confidential
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Infrastructure Placement Guide
If the tag orientation is off by as much as 30°, the range performance is virtually
unaffected. Increasing the angle to 45°, as shown, only reduces the range by 30%. So
at the full power setting of the WherePort, the 20’ range is reduced to 14’. When the
angle reaches 90 degrees however, the tag may not receive the signal from the
WherePort. Although this seems like a severe limitation, it is easily overcome. It does
result in two different approaches to WherePort installation, one for known tag
orientation, and one for random tag orientation.
Interference
Interference can block the magnetic communication from the WherePort to the tag.
The main sources of interference are CRT monitors, motors in heavy machinery, and
other WherePorts. For monitors, don’t expect the WherePort to ping a tag mounted
on a monitor except at very close range. Of course, the monitor must be powered to
present a problem so it is unlikely it will be moving through a WherePort coverage
area while turned on. Monitors operating near to WherePorts do not present a
problem nor will the WherePort interfere with the monitor. On machinery, the tag
must be mounted directly to the motor casing to degrade performance; so do not
mount it there. Expect WherePorts to be the biggest interference problem you find,
mainly due to incorrect installation. WherePorts sharing a common coverage area will
interfere with each other unless the sync lines are connected. Even if the sync lines
are connected, if the WherePorts are not set to the same ID they will interfere with
each other. Setting them to the wrong phase can degrade range and coverage.
Following these guidelines and correct installation will prevent an interference
problem.
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WherePort Placement D0116 rev A1
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WhereNet - Confidential
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